I liked the answer above. Paragraph 2 hits the point in question. Wenatchee (WA) does not allow horns at grade crossings except in an emergency situation. All grade crossings in the city are protected by gates and have warning signs noting that trains do not blow for crossings. Down here in Rock Island, we took a casual look at the same idea. We have a lightly used crossing with lit signs. At minimum we would have to insall (and pay for) crossing gates. That put a stop to that idea.